Navigation Links
Patterning defect-free nanocrystal films with nanometer resolution
Date:8/20/2012

Films made of semiconductor nanocrystals tiny crystals measuring just a few billionths of a meter across are seen as a promising new material for a wide range of applications. Nanocrystals could be used in electronic or photonic circuits, detectors for biomolecules, or the glowing pixels on high-resolution display screens. They also hold promise for more efficient solar cells.

The size of a semiconductor nanocrystal determines its electrical and optical properties. But it's very hard to control the placement of nanocrystals on a surface in order to make structurally uniform films. Typical nanocrystal films also have cracks that limit their usefulness and make it impossible to measure the fundamental properties of these materials.

Now, researchers at MIT say they have found ways of making defect-free patterns of nanocrystal films where the shape and position of the films are controlled with nanoscale resolution, potentially opening up a significant area for research and possible new applications.

"We've been trying to understand how electrons move in arrays of these nanocrystals," which has been difficult with limited control over the formation of the arrays, says physicist Marc Kastner, the Donner Professor of Science, dean of MIT's School of Science and senior author of a paper published online in the journal Nano Letters.

The work builds on research by Moungi Bawendi, the Lester Wolfe Professor of Chemistry at MIT and a co-author of this paper, who was one of the first researchers to precisely control nanocrystal production. Such control made it possible, among other things, to produce materials that glow, or fluoresce, in a range of different colors based on their sizes even though they are all made of the same material.

In the initial phases of the new work, postdoc Tamar Mentzel produced nanoscale patterns that emit invisible infrared light. But working on such systems is tedious, since each fine-tuning has to be checked using time-consuming electron microscopy. So when Mentzel succeeded in getting semiconductor nanocrystal patterns to glow with visible light, making them visible through an optical microscope, it meant that the team could greatly speed the development of the new technology. "Even though the nanoscale patterns are below the resolution limit of the optical microscope, the nanocrystals act as a light source, rendering them visible," Mentzel says.

The electrical conductivity of the researchers' defect-free films is roughly 180 times greater than that of the cracked films made by conventional methods. In addition, the process developed by the MIT team has already made it possible to create patterns on a silicon surface that are just 30 nanometers across about the size of the finest features possible with present manufacturing techniques.

The process is unique in producing such tiny patterns of defect-free films, Mentzel says. "The trick was to get the film to be uniform, and to stick" to the silicon dioxide substrate, Kastner adds. That was achieved by leaving a thin layer of polymer to coat the surface before depositing the layer of nanocrystals on top of it. The researchers conjecture that tiny organic molecules on the surface of the nanocrystals help them bind to the polymer layer.

Such nanocrystal patterns could have many applications, Kastner says. Because these nanocrystals can be tuned not only to emit but also to absorb a wide spectrum of colors of light, they could enable a new kind of broad-spectrum solar cell, he says.

But Kastner and Mentzel's personal interest has more to do with basic physics: Since the minuscule crystals behave almost like oversized atoms, the researchers aim to use the arrays to study fundamental processes of solids, Mentzel says. The success of this technique has already enabled new research on how electrons move in the films.

Such materials could also be used to develop sensitive detectors for tiny amounts of certain biological molecules, either as screening systems for toxins or as medical testing devices, the researchers say.


'/>"/>

Contact: Caroline McCall
cmccall5@mit.edu
Massachusetts Institute of Technology
Source:Eurekalert

Related biology news :

1. Nanocrystal-coated fibers might reduce wasted energy
2. Chemists advance clear conductive thin films
3. High-resolution atomic imaging of specimens in liquid by TEM using graphene liquid cell
4. Citizen scientists to document biodiversity with high-resolution imagery during summer solstice
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/11/2016)... http://www.apimages.com ) - --> http://www.apimages.com ... at AP Images ( http://www.apimages.com ) - Germany ... produce the new refugee identity cards. DERMALOG will be unveiling this ... Hanover next week.   --> ... to produce the new refugee identity cards. DERMALOG will be unveiling ...
(Date:3/9/2016)... NEW YORK , March 9, 2016 ... current and future states of the RNA Sequencing (RNA ... in segments such as instruments, tools and reagents, data ... Analyze various segments of the RNA-Sequencing market such ... RNA-Sequencing services Identify the main factors affecting each segment ...
(Date:3/3/2016)... , March 3, 2016  FlexTech, a SEMI Strategic ... of Innovation, Research & Development, Leadership in Education, and, ... is the 9 th year of the FLEXI ... companies and individuals from past years . Judging ... a pre-described set of criteria, by a panel of ...
Breaking Biology News(10 mins):
(Date:5/25/2016)... CITY, UTAH. (PRWEB) , ... May 25, 2016 , ... ... in healthcare information exchange, today announced that Charles W. Stellar has been named by ... WEDI’s interim CEO since January 2016. As an executive leader with more than 35 ...
(Date:5/25/2016)... ... May 25, 2016 , ... Biohaven Pharmaceutical ... (FDA) has granted the company’s orphan drug designation request covering BHV-4157 for the ... granted by the FDA. , Spinocerebellar ataxia is a rare, debilitating neurodegenerative ...
(Date:5/24/2016)... AVIV, Israel , May 24, 2016   MedyMatch ... providing physicians with artificial intelligence, real-time decision support tools in ... to present at the 2016 Israeli Advanced Technology Industries (IATI) ... of Israel,s 15th National Life Sciences ... 26th at the David Intercontinental Hotel in Tel ...
(Date:5/24/2016)... Rockville, Maryland (PRWEB) , ... May 24, 2016 ... ... introduction of a newly re-branded identity. The new Media Cybernetics corporate branding reflects ... the world of imaging and image analysis. The re-branding components include a crisp, ...
Breaking Biology Technology: